Dependence of DC HTS Cable Critical Current on the Temperature Distribution along the Cable

A temperature of the long HTS cable increases with the temperature of the liquid nitrogen flowing along the cable accumulating the heat load. Therefore, the critical current decreases along the cable and in the part of the cable near outlet becomes the minimum. The critical current of the long HTS cable is estimated by the voltage drop across the cable. The typical n-value of the voltage-current characteristic of the cable is about 10-20. The decreasing of the critical current near the outlet leads the increasing of local electrical losses and it causes consequently the increasing of the local temperature of liquid nitrogen. In spite of the fact, that average electrical field is enough low (E0 = 10-6V/cm) the local current can be higher than the critical one. Measurement of the critical current with criterion of average electrical field cannot provide the safe heat losses value in every part of the cable. In the present paper the local heat generation along the cable and the method for providing the safe local DC heat losses in the every part of the cable are discussed.